Locomotion in an aqueous environment plays an important function in the lives of many micro-organisms, such as bacteria, protozoa, and sperm. Without this kind of self-propelled swimming act, these micro-organisms cannot actively find food, escape predators, or consummate fertilization. Understanding the swimming patterns of these types of motile micro-organisms and the underlying biophysical processes is important to advance existing knowledge in microbiology and has a number of practical applications. For example, it is known that highly motile sperm are generally associated with a higher fertility potential. Highly motile sperm are thought to have a higher quality of sperm which is one factor in successful pregnancies. Tests that are able to discern the quality of sperm are useful in addressing male infertility.
Identifying and quantifying of sperm swimming patterns also has applications for artificial insemination. Artificial insemination has become an indispensable tool in breeding industry of livestock animals, such as cattle, horse, swine and sheep. Currently, most dairy cattle and swine in developed countries are being reproduced through this technique. Although artificial insemination is currently not as widely practiced in the breeding of horses, an increasing number of horse breeders are adapting this new reproduction method as an economical way to enhance the desired traits of their horse breeds. An important factor for successful artificial insemination is to use high-quality semen specimens, especially the specimens containing sperm with high motility. However, most of the evaluations for horse sperm motility have been made using traditional lens-based optical elements. These systems and methods typically have shallow sample holders (˜20 μm deep) to match the restricted depth-of-field of conventional optical microscope objective lenses. Such spatial confinement not only limits the observation of sperms to their two-dimensional (2D) dynamics but also modifies their native three-dimensional (3D) movement.